A mechanical override device is known which is used for overriding the function of an undervoltage coil. The undervoltage coil, during normal operation, is kept in an excited position by an auxiliary power supply derived from the main power supply. In particular, a plunger of the coil, in the excited position, partially protrudes downwards from a coil casing.
While the undervoltage coil is in the excited position, a circuit breaker can be closed or can be kept closed. When the main power supply drops, and thus the auxiliary power supply falls below a prefixed threshold value as well, the coil, which is not longer energized, returns in a non-excited position. In the non-excited position the undervoltage coil prevents the circuit breaker from being closed. In particular, the coil plunger pushes upwards a swinging mechanism by overcoming a force which is opposed by the latter. In this way the electric circuit is opened and is also prevented from being closed.